Patent GB-772434-A (GB)
Title: Improvements in and relating to abrasive materials and articles
IPC: B24D18/00
Filed: 1952-07-28
Abstract: 772,434. Abrasive articles. SIMPSON, H. A. July 21, 1953 [July 28, 1952; Sept. 9, 1952], Nos. 19031/52 and 22618/52. Drawings to Specification. Class 60 An abrasive material or article, such as a disc or wheel, is made up of blocks of abrasive mass having abrasive grain embedded in and bonded to a softer-thanabrasive grain carrying medium, the blocks being separated by non-abrasive material softer than the abrasive grain whereby in use the material or article provides an intermittent abrasive action and wears substantially evenly. The material or article can consist of a sheet or disc of a carrying medium and a bonding medium with or without fillers and/or plasticizers in which definite major groups such as layers or rows of abrasive materials are . arranged. The carrying medium may consist of corrugated materials generally of sheet form, or of cut-lengths or other masses of fibrous or thread-like materials which can be treated as by beating to fray or roughen them so that they can be disposed with their threads interengaged or interlocked to provide an intertwined or felted mass which will withstand the tensile stresses imposed on high speed grinding thereto. Suitable materials for this medium are pieces of woven fibrous material, e.g. cotton, jute or asbestos, pieces of natural fibrous materials such as shredded or otherwise crushed wood or asbestos, wads or threads of natural or synthetic materials such as cotton, wool or nylon, impregnated products such as phenol formaldehyde resin bonded glass fibre or vinyl compounds, metallic threads of steel, copper or brass which may be interwoven as in steel gauze or be made thread-like as in expanded sheet metal, or any mixture of these materials. As an example of suitable woven fibres "corset cuttings" may be used. The free fibre ends or the threads of these materials are interengegad or interkeyed together in the bonding medium or key into the bonding medium and bind the whole mass together. All these materials may be bonded or locked or impregnated by natural glues, whether animal or vegetable, e.g. dextrine, rubber latex or the like. Alternatively synthetic glues such as phenol-cresol formaldehyde phenol formaldehyde resin; urea formaldehyde resins or alkyl or other thermosetting or plastic type glues may be employed, e.g. vinyl resin, or a combination of these glues may be employed. Where a fibrous carrying medium is employed it may be beaten or otherwise treated to fray or roughen the fibrous surfaces so that the fibres become interspaced to form an. intertwined or felted mass; the fibres may be locked or bonded by heat treatment or by employing their solvents in suitable proportions, according to the fibres used. The abrasive materials may be natural, e.g. sand, emery, garnet or synthetic, e.g. aluminous oxide, silicon carbide &c. In making materials or articles such as sheets or discs the carrying medium is wetted if required by any suitable wetting agent such as water or furfurol, and impregnated as by dipping or spraying with the bonding medium. Suitable fillers, e.g. finely divided chalk, wood fibre, slate, coconut shell or bentonite, or plasticizers may be added if desired and the whole thoroughly intermixed as by agitation or stirring to produce a substantially homogenous mix. If the. mix is too bulky or too freely flowing it may be drica until it is in a suitable state for moulding, pressing or otherwise bonding together. Where the bonding material is in powdered form, water, known wetting agents such as furfurol, or solvents such as acetone for spirit soluble resins may be stirred into the mix to produce a cut-lengths mass of the desired viscosity. Lubricants such as camphor, stea rates or wax, plasticizers such as phosphates, e.g. tricresyl phosphate, phthlates, or a mixture of such materials may be added to the mix to assist in producing the desired viscosity and to ensure that the finished discs or the like made from the mix possess the desired degree of flexibility. The mix having been brought to the desired viscosity and tacky state for moulding. pressing or otherwise compressing, is then introduced into moulds and provided mechanically or manually with the rows of layers or other grain formations. These may take any desired configuration, e.g. rows across the mix or spots or blobs of arranged in rows all equispaced in rows or irregularly spaced. The rows whether complete lines or in spots may run substantially. straight across the mix or in curved or crossing lines. In the case of discs the lines may be chords, radial, spiral or other loci. Where blobs or the like are used these may all be the same size of alternate large and small blobs which are staggered in adjacent rows. The abrasive rows, spots &c. may also vary in thickness through the mix. The finished product may be in the form of superposed layers in which the rows, spots &c. are staggered in adjacent layers or run across each other at various angles. In making such materials and articles, the layer is first spread or filled into a mould and the grains are then embedded in it in the desired configuration or the layer may be indented and the grain put in the indentations. Each layer can consist of grain blocks on the surface or embedded in the elements, such blocks being in formations such as rows or spots and built up or preformed to shape for moulding: The form of saw action desired in the finished product dictates the directions in which the blocks of abrasive are orientated. In the case of coarse grain it may be necessary to use filling-in pieces of non- abrasive material between rows, spots or the like of grain. Where corrugated materials are employed they may be made by any suitable process such as by pressing, heating or crimping and may be of paper, card, paper mache or any other suitable substance which will wear away in use leaving the abrasive material exposed.